<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="demo1.css">
    <!-- <style>
        div{
           color: red; 
        }
    </style> -->
</head>
<body>
    <div name="s1" id="a11">我是一个div</div>
    <div>我是一个div</div>
    <div>我是一个div</div>
    <div>我是一个div</div>
    <div>我是一个div</div>
</body>
</html>